Liner system for mines, tunnels and other ground structures

ABSTRACT

A multi-layer liner system is provided, which may be applied using a spray process, where the initial layer facilitates adhesion to the earthen surface (e.g., rock wall surface) and a subsequent layer provides strength and elongation needed to maintain support system integrity even in the case of some rock movement at the wall surface. In one implementation, the initial layer is a structural foam primer layer and the subsequent layer is a fire-resistant top coat layer.

CROSS-REFERENCES

This application claims the benefit of U.S. Provisional Application Ser.No. 61/662,051, filed Jun. 20, 2012, which is incorporated herein byreference.

TECHNICAL FIELD

This application relates generally to systems for protecting againstfalling rock in mines, tunnels and other environments and, moreparticularly, to a sprayable system that is applied to provide suchprotection.

BACKGROUND

One standard process for protecting workers and equipment in mine andtunnel bores against falling rock utilizes a steel mesh that is appliedto the rock surface using bolts. After installation of the steel meshshotcrete is applied. The shotcrete is heavy, slow to dry and tends tocrack as the ground moves behind it.

It would be desirable to provide a light weight system that is rapid todry and flexes as the ground behind it moves, (ii) a system that can beinstalled before or after any steel mesh and bolts are installed orwithout such meshing and/or (iii) a system that can also provideeffective sealing.

SUMMARY

A multi-layer liner system is provided, which may be applied using aspray process, where the initial layer facilitates adhesion to theearthen surface (e.g., rock wall surface) and a subsequent layerprovides strength and elongation needed to maintain support systemintegrity even in the case of some rock movement at the wall surface. Inone implementation, the initial layer is a structural foam primer layerand the subsequent layer is a fire-resistant top coat layer.

The liner system can be used to provide structure support to the earthensurface and/or for sealing of the earthen surface.

The liner system can be used in combination with a mesh structure, whichcan be applied before or after the application of the layers, but canalso be used without such a mesh structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic depiction of the multi-layer support system asapplied to an earthen surface.

FIG. 2 is a schematic cross-section of the liner system with a meshapplied over the liner.

FIG. 3 is a schematic depiction of the liner system with an embeddedmesh.

DESCRIPTION

In one aspect, a method is provided for applying a liner system to anearthen surface such as a mine wall, tunnel bore wall or other earthenwall. The method involves (a) utilizing a plural component spray processto apply a structural foam primer layer in the nature of a firstpolyurethane or polyurea compound onto the earthen surface, the compoundcapable of adhering to wet surfaces; and (b) subsequent to step (a),utilizing a plural component spray process to apply a fire-resistant topcoat layer in the form of a second polyurethane or polyurea compoundthat is different than the first polyurethane or polyurea compound.

In one implementation of the foregoing aspect, the modulus of the of thefirst polyurethane or polyurea compound is higher than the modulus ofthe second polyurethane or polyurea compound, the tensile strength ofthe of the first polyurethane or polyurea compound is lower than thetensile strength of the second polyurethane or polyurea compound, theultimate elongation of the of the first polyurethane or polyureacompound is lower than the ultimate elongation of the secondpolyurethane or polyurea compound and the elastic elongation of the ofthe first polyurethane or polyurea compound is lower than the elasticelongation of the second polyurethane or polyurea compound. The firstlayer will adhere to a variety of surface conditions in an undergroundenvironment, including dry rock and wet/damp rock. The first layer willfill in voids (cracks) in the underground rock faces and will provide a“gluing effect” to prevent loose debris and rock from breaking away fromthe surface. The second coat of the system has the high elongation toallow for rock movement while maintaining the integrity of the supportsystem.

In one implementation, the structural foam primer layer is applied in atleast first, second, third and fourth passes, each from a respectivefirst, second, third and fourth direction, to assure coverage ofirregularities in the earthen surface.

In instance of the foregoing implementation, the fire-resistant top coatlayer is also applied in multiple passes.

In one embodiment, the structural foam primer includes an isocyanate incombination with (i) one or more of an alcohol, a hydroxyl, a polyol oran amine and (ii) a fire retardant and (iii) a foaming agent, and thefire resistant top coat layer includes an isocyanate in combination with(i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii)a fire retardant.

In one implementation of the foregoing method, the structural foamprimer layer is applied at an average thickness of between about 100mils and about 6000 mils, and the fire resistant top coat layer isapplied at an average thickness of between about 100 mils and about 500mils.

In another aspect, a method is provided for applying a support systemthat reduces risk of falling rock or debris from an earthen surface suchas a mine wall, tunnel bore wall or other earthen wall. The methodinvolves (a) utilizing a plural component spray process to apply astructural foam primer layer onto the earthen surface, the structuralfoam primer including an isocyanate in combination with (i) one or moreof an alcohol, a hydroxyl, a polyol or an amine and (ii) a fireretardant and (iii) a foaming agent to create a foaming characteristichaving the ability to adhere to wet surfaces; and (b) subsequent to step(a), utilizing a plural component spray process to apply afire-resistant top coat layer over the structural foam primer layer, thefire resistant top coat layer including an isocyanate in combinationwith (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and(ii) a fire retardant, but not including any foaming agent.

In one implementation of the foregoing method, the structural foamprimer layer is applied at an average thickness of between about 100mils and about 6000 mils, and the fire resistant top coat layer isapplied at an average thickness of between about 100 mils and about 500mils.

In one implementation, the structural foam primer layer has a color thatis distinct from a color of the fire resistant top coat layer, enablinga visible inspection to assure proper coverage.

In one implementation, the method also involves, subsequent to applyingthe fire resistant top coat layer, attaching a mesh retaining structureby applying a plurality of bolts through the fire resistant top layerand the structural foam primer layer and into the earthen surface, andattaching the mesh retaining structure to the bolts.

In another implementation, prior to applying the structural foam primerlayer, a mesh retaining structure is applied by applying a plurality ofbolts into the earthen surface, and attaching the mesh retainingstructure to the bolts.

In one embodiment, the isocyanate of the structural foam primer layer isa diisocyanate and the isocyante of the fire resistant top coat later isa diisoycanate.

In one implementation of the foregoing embodiment, the diisocyanate ofthe structural foam primer layer is 4,4-diphenylmethane diisocyanate,and the diisocyanate of the fire resistant top coat layer is selectedfrom the group consisting of isophorone diisocyanate, methylene diphenyldiisocyanate, toluene diisocyanate or hexamethylene diisocyanate.

In one implementation, the strength of the fire resistant top coat layeris greater than the strength of the structural foam primer layer.

When properly applied, the structural foam primer layer may fill smallcracks in the earthen surface and adheres earthen material on oppositesides of such cracks together.

In another aspect, a liner system applied to an earthen surface of amine wall, tunnel bore wall or other earthen wall includes a pluralcomponent structural foam primer layer adhered to the earthen surface,the structural foam primer including an isocyanate in combination with(i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii)a fire retardant and (iii) a foaming agent; and a plural componentfire-resistant top coat layer over the structural foam primer layer, thefire resistant top coat layer including an isocyanate in combinationwith (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and(ii) a fire retardant, but not including any foaming agent.

The structural foam primer layer may have an average thickness ofbetween about 100 mils and about 6000 mils, and the fire resistant topcoat layer has an average thickness of between about 100 mils and about500 mils. However, variations are possible depending upon a variety offactors such as surface profile (depth of voids in the rock surface),desired visual appearance, or variable in engineering of the appliedsystem.

The structural foam primer layer may have a color that is distinct froma color of the fire resistant top coat layer. During installation, thiscolor difference can be observed by the installer, or by a subsequentinspector, to verify the continuity and completeness of the linersystem.

A mesh retaining structure (e.g., wire mesh) may be located to theexterior of the fire resistant top coat layer. A plurality of bolts maybe used to attach the mesh, where the bolts extend through the fireresistant top coat layer and the structural foam primer layer and intothe earthen surface. Holes may be drilled through the layers and intothe earthen surface in order to received such bolts. Alternatively, themesh retaining structure may be applied prior to spraying of the layers,such that the mesh is embedded at least partially within one or both ofthe structural foam primer layer and/or the fire resistant top coatlayer. In some case the mesh may not be used at all.

The isocyanate of the structural foam primer layer may be a diisocyanateand the isocyante of the fire resistant top coat later may be adiisoycanate. By way of example, the diisocyanate of the structural foamprimer layer is 4,4-diphenylmethane diisocyanate, and the diisocyanateof the fire resistant top coat layer is selected from the groupconsisting of isophorone diisocyanate, methylene diphenyl diisocyanate,toluene diisocyanate or hexamethylene diisocyanate. By way of example,the primary layer may be Custom Linings Structural Foam Primer and thetop coat layer may be Custom Linings 711 FR Fire Resistant Lining, bothavailable from Custom Linings, Inc. of Beuna Vista, Colo.

Referring now to FIG. 1, a schematic depiction of the liner system 10 asapplied to an earthen surface 12 is shown, with the structural foamprimer layer 14 shown having an average thickness that is generally atleast two times, and preferably at least three times, the averagethickness of the fire resistant top coat layer 16. An exemplary pluralcomponent spraying nozzle system is shown at 18. The liner system ofFIG. 1 is applied without the use of any mesh. However, as per FIG. 2 amesh 20 (e.g., wire mesh) may be applied over the two layers after theyare applied by drilling holes through the layers and into the earthensurface, in which bolts 22 (e.g., rock bolts) are applied to secure themesh 20 in place. In another variation per FIG. 3, the bolts 22 and meshare applied before the two layers, in which case the bolts and meshbecome fully or partially embedded in the layers.

The method and system described above provides advantages over knownshotcrete liner systems. For example, the layers of the present systemcure rapidly (e.g., within minutes), providing for a much more rapidspeed of installation. The materials utilized also enable application ofthe liner system to frozen wall surfaces. Moreover, as previouslysuggested, the present liner system and method can be implemented suchthat the layers are applied before any application of bolts and mesh,thereby reducing risk of earthen material falling during the applicationof such bolts and mesh.

As used herein, the term plural component processing technique meansblending two or more chemicals together in a specific or varying ratiowith either direct impingement equipment, equipment utilizing a staticmixer assembly to mix/bled the chemicals or by mixing in an opencontainer by hand or by other mechanical mixing method to producematerial that cures to some degree. In the illustrated embodiment, animpingement mix spray process is shown using a spray mechanism 18.

In order to most effectively provide adequate coverage of irregularsurfaces (e.g., surfaces with jutting or protruding angular rockstructure), the layers may be applied in multiple passes havingdifferent spray directions. Generally, at least four passes with atleast for different spray directions are desired (e.g., one pass with aleft to right movement, where the spray is direction at forty-fivedegree angle in the direction of movement, one pass with a right to leftmovement, where the spray is direction at forty-five degree angle in thedirection of movement, one pass one pass with a top to bottom movement,where the spray is direction at forty-five degree angle in the directionof movement, and one pass with a bottom to top movement, where the sprayis direction at forty-five degree angle in the direction of movement).

It is to be clearly understood that the above description is intended byway of illustration and example only and is not intended to be taken byway of limitation, and that changes and modifications are possible.

What is claimed is:
 1. A method of applying a liner system to an earthensurface such as a mine wall, tunnel bore wall or other earthen wall,comprising: (a) utilizing a plural component spray process to apply astructural foam primer layer in the nature of a first polyurethane orpolyurea compound onto the earthen surface, the compound capable ofadhering to wet surfaces; and (b) subsequent to step (a), utilizing aplural component spray process to apply a fire-resistant top coat layerin the form of a second polyurethane or polyurea compound that isdifferent than the first polyurethane or polyurea compound.
 2. Themethod of claim 1 wherein the modulus of the of the first polyurethaneor polyurea compound is higher than the modulus of the secondpolyurethane or polyurea compound, the tensile strength of the of thefirst polyurethane or polyurea compound is lower than the tensilestrength of the second polyurethane or polyurea compound, the ultimateelongation of the of the first polyurethane or polyurea compound islower than the ultimate elongation of the second polyurethane orpolyurea compound and the elastic elongation is of the of the firstpolyurethane or polyurea compound is lower than the elastic elongationof the second polyurethane or polyurea compound.
 3. The method of claim1 wherein the structural foam primer layer is applied in at least first,second, third and fourth passes, each from a respective first, second,third and fourth direction, to assure coverage of irregularities in theearthen surface.
 4. The method of claim 3 wherein the fire-resistant topcoat layer is applied in multiple passes.
 5. The method of claim 4wherein the structural foam primer layer is applied with an averagethickness that is at least 3 times greater than an average thickness ofthe applied fire-resistant top coat layer.
 6. A method of applying aliner system to an earthen surface such as a mine wall, tunnel bore wallor other earthen wall, comprising: (a) utilizing a plural componentspray process to apply a structural foam primer layer onto the earthensurface, the structural foam primer including an isocyanate incombination with (i) one or more of an alcohol, a hydroxyl, a polyol oran amine and (ii) a fire retardant and (iii) a foaming agent to create afoaming characteristic having the ability to adhere to wet surfaces; (b)subsequent to step (a), utilizing a plural component spray process toapply a fire-resistant top coat layer over the structural foam primerlayer, the fire resistant top coat layer including an isocyanate incombination with (i) one or more of an alcohol, a hydroxyl, a polyol oran amine and (ii) a fire retardant, but not including any foaming agent.7. The method of claim 6 wherein: the structural foam primer layer isapplied at an average thickness of between about 100 mils and about 6000mils; and the fire resistant top coat layer is applied at an averagethickness of between about 100 mils and about 500 mils.
 8. The method ofclaim 6 wherein the structural foam primer layer has a color that isdistinct from a color of the fire resistant top coat layer.
 9. Themethod of claim 6, further comprising: (c) subsequent to step (b),attaching a mesh retaining structure by applying a plurality of boltsthrough the fire resistant top layer and the structural foam primerlayer and into the earthen surface, and attaching the mesh retainingstructure to the bolts.
 10. The method of claim 6, further comprising:(c) prior to step (a), attaching a mesh retaining structure by applyinga plurality of bolts into the earthen surface, and attaching the meshretaining structure to the bolts.
 11. The method of claim 6 wherein theisocyanate of the structural foam primer layer is a diisocyanate and theisocyante of the fire resistant top coat later is a diisoycanate. 12.The method of claim 11 wherein: the diisocyanate of the structural foamprimer layer is 4,4-diphenylmethane diisocyanate; the diisocyanate ofthe fire resistant top coat layer is selected from the group consistingof isophorone diisocyanate, methylene diphenyl diisocyanate, toluenediisocyanate or hexamethylene diisocyanate.
 13. The method of claim 6wherein a strength of the fire resistant top coat layer is greater thana strength of the structural foam primer layer.
 14. The method of claim6 wherein the structural foam primer layer fills small cracks in theearthen surface and adheres earthen material on opposite sides of suchcracks together.
 15. The method of claim 6 wherein the earthen surfacehas a temperature of zero degrees Centigrade or lower.
 16. A linersystem applied to an earthen surface of a mine wall, tunnel bore wall orother earthen wall, the liner system comprising: a plural componentstructural foam primer layer adhered to the earthen surface, thestructural foam primer including an isocyanate in combination with (i)one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) afire retardant and (iii) a foaming agent; a plural componentfire-resistant top coat layer over the structural foam primer layer, thefire resistant top coat layer including an isocyanate in combinationwith (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and(ii) a fire retardant, but not including any foaming agent.
 17. Thesystem of claim 16 wherein: the structural foam primer layer has anaverage thickness of between about 100 mils and about 6000 mils; and thefire resistant top coat layer has an average thickness of between about100 mils and about 500 mils.
 18. The system of claim 16 wherein thestructural foam primer layer has a color that is distinct from a colorof the fire resistant top coat layer.
 19. The system of claim 16,further comprising: a mesh retaining structure located to the exteriorof the fire resistant top coat layer and attached via a plurality ofbolts that extend through the fire resistant top coat layer and thestructural foam primer layer and into the earthen surface.
 20. Thesystem of claim 16, further comprising: a mesh retaining structureembedded at least partially within one or both of the structural foamprimer layer and/or the fire resistant top coat layer.
 21. The system ofclaim 16 wherein the isocyanate of the structural foam primer layer is adiisocyanate and the isocyante of the fire resistant top coat later is adiisoycanate.
 22. The system of claim 21 wherein: the diisocyanate ofthe structural foam primer layer is 4,4-diphenylmethane diisocyanate;the diisocyanate of the fire resistant top coat layer is selected fromthe group consisting of isophorone diisocyanate, methylene diphenyldiisocyanate, toluene diisocyanate or hexamethylene diisocyanate. 23.The system of claim 16 wherein a strength of the fire resistant top coatlayer is greater than a strength of the structural foam primer layer.24. The system of claim 16 wherein the structural foam primer layerfills small cracks in the earthen surface and adheres earthen materialon opposite sides of such cracks together.